1. Field of the Invention
The present invention relates to a light emitting semiconductor device having such light emitting devices as light emitting diodes (LEDs) or the like having pn junctions, said light emitting devices being integrated in the same semiconductor body.
2. Description of Related Art
An example of conventional light emitting semiconductor devices has been disclosed in a reference literature "Hakkou-daiodo" (Light Emitting Diode) (pp.27 to 30 by OKUNO, issued by Sangyo Tosho Inc. 1994). FIG. 14 is a sectional view showing the structure of LEDs in a conventional light emitting semiconductor device. An LED shown in FIG. 14(A) is composed of a semiconductor body 10 having a homo-junction by an n-type GaP layer 12/a p-type GaP layer 13, the homo-junction being formed on a GaP substrate 11, a p side electrode 14 to be an individual electrode of each LED, and an n side electrode 15 to be a common electrode to plural LEDs, wherein this homo-junction interface is a pn junction interface 16.
An LED shown in FIG. 14(B) is composed of a semiconductor body 20 having a single hetero-junction of a p-type Al.sub.x Ga.sub.1-x As (x=0.35) layer 22/an n-type Al.sub.x Ga.sub.1-x As (x=0.65) layer 23, the single hetero-junction being formed on a GaAs substrate 21, an n side electrode 24 to be an individual electrode, and a p side electrode 25 to be a common electrode, wherein this hetero-junction interface is a pn junction interface.
An LED shown in FIG. 14(C) is composed of a semiconductor body 30 having a double hetero-junction of a p-type Al.sub.x Ga.sub.1-x As (x=0.65) layer 31/a p-type Al.sub.x Ga.sub.1-x As (x=0.65) layer 22/an n-type Al.sub.x Ga.sub.1-x As (x=0.65) layer 23, an n side electrode 24, and a p side electrode 25, wherein the hetero-junction interface of the AlGaAs (x=0.35) layer 22/the AlGaAs (x=0.65) layer 23 is a pn junction interface.
In case of the LEDs shown in FIGS. 14(B) and 14(C) each of which has a hetero-junction, an emitted light has a wavelength corresponding to the energy band gap of the p-type AlGaAs (x=0.65) layer 22 which is a light emitting layer.
However, an LED of these conventional semiconductor devices emits a light having a determined single wavelength, and in these conventional structures an integration density of LEDs having different wavelengths is at most 600 dpi and it has been difficult to integrate the LEDs in a higher density than 600 dpi.